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991.
Yoshito Ohtake Yoshimasa Yamamoto Mio Gonokami Tsutomu Nakamura Hiroyuki Ishii Seiichi Kawahara 《Polymer Degradation and Stability》2013
The degradation of an ethylene–propylene-diene (EPDM) rubber seal used in a water supply system was investigated using focused ion beam-scanning electron microscopy (FIB-SEM). The EPDM rubber seal was used for 3 years within the temperature range 20–40 °C in a city water system. The accretions present on the surface of the EPDM seal after use were observed by SEM and were found to consist of iron and oxygen atoms based on energy dispersive X-ray spectroscopy (EDS) analysis. A cross-sectional depth image of the EPDM rubber was obtained by FIB-SEM, after slicing the EPDM rubber with a focused Gallium ion beam. Iron and oxygen atoms in the cross-section of the EPDM rubber were detected through EDS. The distribution of iron was comparable to that of oxygen derived from the carbonyl groups generated by the degradation of EPDM, suggesting that iron ions may promote the degradation of natural rubber through catalytic effects. 相似文献
992.
Mutagenic and carcinogenic heterocyclic amines (HCAs) are formed during heating of various proteinaceous foods, but human exposure to HCAs has not yet been elucidated in detail. To assess long-term exposure to HCAs, we developed a simple and sensitive method for measuring HCAs in hair by automated on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). Using a Zorbax Eclipse XDB-C8 column, 16 HCAs were analyzed within 15 min. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL sample at a flow rate of 200 μL min−1 using a Supel-Q PLOT capillary column as an extraction device. The extracted HCAs were easily desorbed from the column by passage of the mobile phase, with no carryover observed. This in-tube SPME LC–MS/MS method showed good linearity for HCAs in the range of 10–2000 pg mL−1, with correlation coefficients above 0.9989 (n = 18), using stable isotope-labeled HCA internal standards. The detection limits (S/N = 3) of 14 HCAs except for MeAαC and Glu-P-1 were 0.10–0.79 pg mL−1. This method was successfully utilized to analyze 14 HCAs in hair samples without any interference peaks, with quantitative limits (S/N = 10) of about 0.17–1.32 pg mg−1 hair. Using this method, we evaluated the exposure to HCAs in cigarette smoke and the suitability of using hair HCAs as exposure biomarkers. 相似文献
993.
Hiroyuki Kojima Chisato Takahata David Lemin Masato Takahashi Takuya Kumamoto Waka Nakanishi Noriyuki Suzuki Tsutomu Ishikawa 《Helvetica chimica acta》2013,96(3):379-388
An aziridinomitosene skeleton, a basic core of mitomycin antibiotics, was straightforwardly prepared from N‐(p‐toluenesulfonyl)indole‐2‐carboxaldehyde in 16% overall yield by successive reactions of guanidinium ylide‐mediated aziridination, InCl3‐catalyzed epimerization of trans‐3‐(indol‐2‐yl)aziridine‐2‐carboxylate, leading to the cis‐derivative, and dehydrative cyclization. 相似文献
994.
Tsutomu Oishi Minoru Fujimoto Toshizumi Hirota Shoji Kajigaeshi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):687-696
9-Fluorenyl (FMA) and 9-phenyl-9-fluorenyl methacrylates (PFMA) were prepared from methacryloyl chloride with 9-fluorenol and from silver methacrylate with 9-phenyl-9-fluorenyl chloride, respectively. The polymerizations of FMA and PFMA were studied by using α,α′-azobisisobutyronitrile (AIBN), n-butyllithium (n-BuLi), and n-BuLi-(?)-sparteine (Sp) complex in toluene and tetrahydrofuran (THF). Only PFMA polymers obtained with the n-BuLi-Sp complex showed a specific rotation ([α]D 21 ?3 to ?16° in THF). The number-average molecular weights of the FMA and PFMA polymers were 7 700-16 900 and 1 400-4 700, respectively. 相似文献
995.
996.
Dipl.‐Chem. Crispin Lichtenberg Prof. Dr. Jun Okuda 《Angewandte Chemie (International ed. in English)》2013,52(20):5228-5246
Organometallic allyl compounds are important as allylation reagents in organic synthesis, as polymerization catalysts, and as volatile metal precursors in material science. Whereas the allyl chemistry of synthetically relevant transition metals such as palladium and of the lanthanoids is well‐established, that of main group metals has been lagging behind. Recent progress on allyl complexes of Groups 1, 2, and 12–16 now provides a more complete picture. This is based on a fundamental understanding of metal–allyl bonding interactions in solution and in the solid state. Furthermore, reactivity trends have been rationalized and new types of allyl‐specific reactivity patterns have been uncovered. Key features include 1) the exploitation of the different types of metal–allyl bonding (highly ionic to predominantly covalent), 2) the use of synergistic effects in heterobimetallic compounds, and 3) the adjustment of Lewis acidity by variation of the charge of allyl compounds. 相似文献
997.
Tsutomu Tsuchiya Yoshiaki Takahashi Makoto Endo Sumio Umezawa Hamao Umezawa 《Journal of carbohydrate chemistry》2013,32(4):587-611
2′,3′-Dideoxy-2′-fluorokanamycin A (23) was prepared by condensation of 6-azido-4-0-benzoyl-2,3,6-trideoxy-2-fluoro-α-D-ribo-hexopyranosyl bromide (13) and a protected disaccharide (19). Methyl 4,6-0-benzylidene-3-deoxy-β-D-arabino-hexopyranoside (5) prepared from methyl 4,6-0-benzylidene-3-chloro-3-deoxy-β-D-allo-hexopyranoside (1) by oxidation with pyridinium chlorochromate followed by reduction with Na2 S2O4 was fluorinated with the DAST reagent to give methyl 4,6-O-benzylidene-2,3-dideoxy-2-fluoro-β-D-ribo-hexopyranoside (7). Successive treatment of 7 with NBS, NaN3 and SOBr2 gave 13. The structure of the final product (23) was determined by the 1H and 19F and shift-correlated 2D NMR spectra. 相似文献
998.
999.
1000.
M. Dangelo M. Konishi I. Matsuda C. Liu S. Hasegawa T. Okuda T. Kinoshita 《Surface science》2005,590(2-3):162-172
We report the first scanning tunneling microscopy (STM) and core-level photoemission (CL-PES) studies of a structure induced by sub-monolayer Na deposition on the Si(1 1 1) surface. In the filled-state STM images, five bright protrusions in the unit cell are located on the Ag trimers of the structure. The Si 2p core-level photoemission decomposition shows that the surface-shifted component originated from the Si-trimer atoms in the surface splits into two for the structure, which are attributed to the Si-trimer atoms in the unit cell which are affected and unaffected by the Na adsorption. These results show strong similarities between the Na-induced superstructure and the noble metal-induced ones, indicating a common atomic structure and formation mechanism. 相似文献